This paper presents the results of a long-term study on trace elements content in the ectohumus horizons (O) and the mineral horizons (A or A/B) of the Puszcza Kampinoska Biosphere Reserve soils. Studied were the trace elements: Mn, Pb, Zn, Cu, Ni, Cr, Co. It was found that the mineral horizons of the soils contain natural amounts of the heavy metals; an increased concentration of Pb, Zn and Cu was found in ectohumus in some localities and dates. The observed years-long trend of the studied metals concentration has recently been diminishing. The recommended earlier critical values for forest ectohumus were confirmed.